Computers, computer networks, and other computer-based systems are becoming increasingly important as part of the infrastructure of everyday life. Networks are used for sharing peripherals and files. In such systems, complex components are the most common sources of failure or instability. The proliferation of multiple interacting components leads to problems that are difficult or impossible to predict or prevent. The problems are compounded by the use of networks, which introduce the added complexity of multiple machines interacting in obscure and unforeseen ways.
Most complex electronic devices, including computer systems and networked hardware, are designed with built-in diagnostics. These diagnostics are specifically designed for the system and usually detect a fairly wide range of problems. Sometimes they can also implement fixes or workarounds, or at least pinpoint a problem to speed its repair.
The use of interconnected components, although advantageous for performance and expandability, increases the risk of an error propagating through the system and causing widespread harm in the system.
For example, Fibre Channel (“FC”) is a high performance, serial interconnect standard for bi-directional, point-to-point communications between servers, storage systems, workstations, switches, and hubs. Fibre Channel standards are described by the Fibre Channel Industry Association (FCIA) (http:/www.fibrechannel.org). FC supports a variety of upper-level protocols, including the small computer systems interface (“SCSI”) protocol. A device is linked to the network through an FC port and copper wires or optical fibres. An FC port includes a transceiver and an interface controller, which conducts lower-level protocol exchanges between the FC channel and the device in which the FC port resides.
Because of the high bandwidth and flexible connectivity provided by FC, FC is a common medium for interconnecting devices within multi-peripheral-device enclosures, such as redundant arrays of inexpensive disks (“RAIDs”), and for connecting multi-peripheral-device enclosures with one or more host computers. These multi-peripheral-device enclosures economically provide greatly increased storage capacities and built-in redundancy that facilitates mirroring and fail over strategies needed in high-availability systems. Although FC is well-suited for this application with regard to capacity and connectivity, FC is a serial communications medium. Malfunctioning peripheral devices and enclosures can, in certain cases, degrade or disable communications. FC-based multi-peripheral-device enclosures are expected to isolate and recover from malfunctioning peripheral devices.